Corotrons are frequently used in electrographic printing apparatuses in order to generate an electrical field with which photoconductor elements, transfer elements or recording media (for example) have their charges reversed.
As an example, from US 2008/0205920 A1 an electrographic printing apparatus is known with which a printing substrate is printed simultaneously on both sides. Toner images are generated in a same manner in an upper printing group and lower printing group and are transfer-printed onto the printing substrate in a transfer printing station. In order to be able to simultaneously transfer-print the toner images onto the printing substrate, the toner images on a transfer belt must have their charges reversed. For this a corotron made of a corotron shield and a corotron wire is used that is arranged adjacent to a roller around which the transfer belt is deflected. Refer to US 2008/0205920 A1 for details and US 2008/0205920 A1 is incorporated herein by reference.
The efficiency of the charge reversal depends on, among other things, a charge reversal current. This is directed from the corotron via ionized air to the transfer belt, where it reverses the charge of the toner image, and finally discharges via the roller. A distance between the corotron element and the roller is decisive for a voltage at the corotron shield and the roller.
Since the distance between the corotron element and the roller has an effect on the print quality, it is important that the distance between corotron element and roller is maintained.